How fast is fast enough??

With all these Sandisk memory cards I've been looking at I'm seeing that Ultra II has a 9mb/sec write speed, Extreme III is 20mb/sec, and Extreme IV is 40mb/sec.

With my Canon Rebel XT how fast does a memory card need to be in order for my camera to be able to use it to its full potential. I mean...if my camera can't take 40mb of information in a second then there is no point in having a memory card that can store info that fast right?

Can anyone shed some light on the subject for me??

Thanks!!

You probably won't notice a difference in speed until you are shooting fast enough to stuff the buffer, then have to wait for it to download and make room for your next shots. If that's the case, then you'll quickly notice speed differences. If you seldom find yoursel waiting for the buffer, you won't notice a faster card.

Kyle - Rob Galbraith happened to use an XT to test the speed of a bunch of cards a while back.

http://www.robgalbraith.com/bins/multi_page.asp?cid=6007-7699

I don't think that you will be filling up you buffer fast enough to tell a difference. Although if you did the math it would seem that you need a card 25mb/sec or higher.(The TX can shoot up to 3 frames per sec with the average RAW file at at 8.3MB. So 8.3MB x 3sec = 24.9MB/sec.) But the fact that your buffer can hold the images while it is waiting to write it to the card means that you will not see the difference unless you plan on taking 100 pictures in a couple of minutes.

I think that the only time that you are going to see a big difference is when you transfer the picture to your computer, but then again I do not think that it is worth the extra money.

I frequently filled the buffer on my XTi, shooting jpg + raw in burst mode for birds in flight. The buffer filled after 8-9 shots.

So I would say, especially since you shoot birds, the faster the card, the better.

I'll say from my own XT, that I've noticed no difference in buffer clearing times between the Ultra II and faster cards like the Lexar Pro 80X and Kingston Ultimate 133X. This camera just can't take advantage of the card speed. The XTi might be able to. I'm not sure.

But the faster cards read faster on my PC when it comes to that, so there is some advantage there.

Mel-

I read an article on storage cards recently and memory serves me correctly, the camera controls the write speed to the card. the speed of the card controls the upload speed to your computer.
Can someone comfirm this.
therefore, if you've taken 500 Raw files at 5Mb each , how long it will take to upload 2500 Mbs will be based on this delivery speed and factored by the upload method, USB 1 or 2 or firewire.

Fred - That isn't quite correct. It may usually be the case, but only because of how the hardware tends to work, not because of any purposeful reason.

The camera will write to the card as fast as it can - the limit could be caused by the card, or the camera. The same holds true when writing from the card to your hard drive. Theoretically, the limit could be the card/reader, or it could be your computer.

However, in practice, the fastest cards are capable of being written faster than any (normal) camera can write them. And your computer is capable of being written faster than any card reader can write. So the limiting factors end up being what you said - camera limited when taking pics and card/reader limited when loading them onto your computer.

If you have a slow card (or really old PC?), however, this might not be true.

Thanks for the up date and i hope this helps Kyle with his original question and concern. it has helped me. i use a Macbook Pro core 2 duo and 5D. so i buy the fastest CF cards available.

http://www.juzaphoto.com/eng/articles/compact_flash_cards_tests.htm

Thanks for the up date and i hope this helps Kyle with his original question and concern. it has helped me. i use a Macbook Pro core 2 duo and 5D. so i buy the fastest CF cards available.